Fix text in C++ default statement

[Crayon2000]

Description

• Fix text in C++ default statement
• Fix some typos in comments

Related Issue

None that I know of.

Motivation and Context

It fixes an error in the C++ output code. Problem was introduced in PR #2431.

How Has This Been Tested?

Tested with this command: quicktype --lang cpp --src-lang json ./test/inputs/json/samples/us-senators.json

Previous Behaviour / Output

Before the changes we can see that we are getting a [object Object] for all enumeration names:

    inline void to_json(json & j, const SenatorRankLabel & x) {
        switch (x) {
            case SenatorRankLabel::JUNIOR: j = "Junior"; break;
            case SenatorRankLabel::SENIOR: j = "Senior"; break;
            default: throw std::runtime_error("Unexpected value in enumeration \"[object Object]\": " + std::to_string(static_cast<int>(x)));
        }
    }

    inline void from_json(const json & j, Title & x) {
        if (j == "Sen.") x = Title::SEN;
        else { throw std::runtime_error("Input JSON does not conform to schema!"); }
    }

    inline void to_json(json & j, const Title & x) {
        switch (x) {
            case Title::SEN: j = "Sen."; break;
            default: throw std::runtime_error("Unexpected value in enumeration \"[object Object]\": " + std::to_string(static_cast<int>(x)));
        }
    }

New Behaviour / Output

After the changes, we get the proper enumeration names:

    inline void to_json(json & j, const SenatorRankLabel & x) {
        switch (x) {
            case SenatorRankLabel::JUNIOR: j = "Junior"; break;
            case SenatorRankLabel::SENIOR: j = "Senior"; break;
            default: throw std::runtime_error("Unexpected value in enumeration \"SenatorRankLabel\": " + std::to_string(static_cast<int>(x)));
        }
    }

    inline void from_json(const json & j, Title & x) {
        if (j == "Sen.") x = Title::SEN;
        else { throw std::runtime_error("Input JSON does not conform to schema!"); }
    }

    inline void to_json(json & j, const Title & x) {
        switch (x) {
            case Title::SEN: j = "Sen."; break;
            default: throw std::runtime_error("Unexpected value in enumeration \"Title\": " + std::to_string(static_cast<int>(x)));
        }
    }

[Crayon2000]

For some reason the 'objective-c' test never run. Should I do something about this so my PR can be merged?